The present invention relates to the field of furnaces for the thermal treatment of solid materials, and more particularly to pyrolysis (or thermolysis) furnaces intended for treating solids such as waste of all kinds.
The furnaces concerned are generally cylindrical and rotate about their axis of symmetry. The heat input necessary for pyrolysis can consist of solids or of gases in contact or not with the solids to be treated.
Patent application FR-2,668,774 thus describes a pyrolysis furnace in which heating can be performed outside the furnace by pyrolysis gas-fed burners; according to another embodiment, heat-carrying solids are brought into contact with the waste to be pyrolyzed inside the furnace. An additional reactor is then necessary for heating the heat-carrying solids.
This type of installation entails a complex implementation and proves to be a big energy consumer.
Furthermore, the numerous connections make the installation more costly, less reliable and above all decrease its thermal efficiency.
One way of solving partly these problems consists for example in making the furnace more compact. Document DE 29 03 280 discloses a compact rotary furnace in which the waste to be treated passes successively through a first rotary cylinder, then through a rotary ring coaxial to the cylinder. The waste is heated by heat-carrying gases circulating around the cylinders. An external rotating jacket delimits the heating zone.
Although it allows, by its compactness, to obtain a higher thermal efficiency, this type of installation remains complex, notably at the level of the shape of the cylinders; furthermore, since the heating means and the fumes discharge means are not stationary, problems may arise at the level of the connections. This type of installation, like most of the known rotary furnaces, must be considered as external indirect heating rotary furnaces.